Project Summary: My long-term goal is to improve public health by identifying the signaling pathways that regulate brain development, a critical pursuit given the putative developmental origin of many neurological disorders. This will be accomplished by elucidating mechanisms through which genes associated with neurodevelopmental disorders disrupt the migration and synaptic integration of neurons into circuits. The short-term goal of this project is to preform training and research to investigate the receptor tyrosine kinase, KitR. Mutations in KitR have been identified in intellectual disability and in autism. While KitR signaling is critical to the development and physiology of diverse peripheral tissues, and while KitR is abundantly expressed in the central nervous system, little is known about how KitR regulates brain development. I propose to address this knowledge gap using the mouse cerebellum as a model system due to the high and similar expression of KitR in human and mouse cerebella and due to the experimental and genetic tractability of the mouse. Within the cerebellum, it has been observed that Kit Ligand (KitL) is expressed postsynaptically by Purkinje cells (PCs), while KitR is expressed presynaptically by Molecular Layer Interneurons (MLIs). Specific Aim 1, in the K99 phase, is to test the hypothesis that KitL attracts the developmental migration of MLIs to PCs. Specific Aim 2, in the K99 Phase, is to test the hypothesis that MLI KitR regulates innervation of PCs. Specific Aim 3, in the R00 phase, is to determine the KitR effector pathways regulating MLI migration and synaptogenesis, and to determine how an autism linked KitR mutation impacts these processes. These Aims will be accomplished by stereotaxic cerebellar injection of viral particles into perinatal mice to knockout, mis-express, or knockout and re-express mutant forms of, KitL or KitR. The impacts on the distribution, form, and synaptic connectivity of KitL/R manipulated neurons will be assayed by stereological/morphometric analyses and by electrophysiological interrogation of MLI/PC connectivity. The training plan addresses my specific technical deficit in electrophysiology through internal and external training, courses, and consultants. I propose training from two mentors: a young investigator specializing in viral approaches to study autism associated genes in synaptogenesis, and an established investigator with a record of transitioning trainees to permanent research positions and expertise in electrophysiology and neuron migration. The proposed research will take place at Dartmouth College, which, as evidenced in Facilities, Equipment, Environment, and in preliminary data, has all the resources to conduct the proposed studies, which will serve NIMH Research Priority 1.1 to ?Determine the molecular, cellular, and systems components underlying brain connectivity?.